This invention relates to fiber network structures. More particularly, this invention relates to three-dimensionally shaped fiber network structures which are resilient and have improved softness, comfort and aesthetic properties. The present invention further relates to improved methods of making such network structures and to articles containing such structures.
The shaping or molding of textiles into three-dimensional structures is well known in the art. Examples include the shaping of felt hats, the molding of upholstery fabrics to conform to the shapes of chairs, and permanent press treatments. In most applications, the softness and comfort of traditional textile materials is desirable. Consequently, molded fabrics are usually soft and drape well.
Methods for shaping or molding textile materials to form three-dimensional structures are disclosed, for example, in U.S. Pat. Nos. 3,434,478; 3,981,310; 4,667,490; 4,128,684; 4,631,221; 4,890,877; 5,364,686; 5,158,821; and 5,447,776.
U.S. Pat. Nos. 3,434,478; 3,981,310 and 4,667,490 disclose the addition of small-diameter monofilament yarns to lingerie fabrics to improve shape retention in molded brassiere cups. The monofilaments taught in these references have denier values of from 16 to 25, which corresponds to diameters of from 40 to 50 microns.
U.S. Pat. No. 4,128,684 discloses pleated or corrugated fabrics for use in air conditioning heat exchangers and chemical reactors. These fabrics are formed from woven fabrics containing both multifilament and monofilament yarns. The fabrics are pleated or corrugated to provide continuous open flow channels parallel to the fabric surface. The multifilament fabric provides controlled capillary flow across the fabric. The monofilament yarns are stiff enough to hold the channels open provided they have been adequately heatset in the pleated configuration. Ideally, the monofilaments are heated above their softening temperatures so that the bond to adjacent fibers assures fabric stability. While these fabrics have adequate stiffness to make the flow channels self-supporting, the pleated structure is a poor load-bearing structure. Pleated structures characteristically collapse by returning to their flat configuration. This form of collapse is catastrophic, that is, once the yield load has been exceeded, the compression modulus turns negative and total collapse is inevitable.
Three-dimensionally shaped fiber network structures made from textile fabrics which have been impregnated with a thermoset polymer and then molded into the desired shape are disclosed, for example, in U.S. Pat. Nos. 4,631,221; 4,890,877; 5,158,821; and 5,447,776.
The properties of three-dimensionally shaped fiber network structures derived from conventional textile-type yarns depend primarily on the type and quantity of thermoset resin used. The more resin that is used, the stiffer the network. In general, such three-dimensional structures tend to be stiff and brittle, and are intended for use mainly as lightweight structural materials. These three-dimensional structures suffer yield and permanent deformation if compressed beyond 10 to 20%.
Three-dimensional fiber network structures have also been formed using multifilament yarns with two thermoplastic polymers of different melting temperatures, wherein bonding is achieved by melting only the lower melting temperature thermoplastic polymer. Such a structure is taught, for example, in U.S. Pat. No. 5,364,686. However, such fiber network structures tend to be stiff and to suffer permanent deformation when compressed beyond 10 to 20%.
More recently, resin-free three-dimensional network structures have been developed which are based on large-diameter monofilaments. Reference is made, for example, to copending, commonly assigned U.S. patent application Ser. No. 08/577,655 to Kim et al., filed Dec. 22, 1995. Such fiber network structures consist essentially of thermoplastic polymer monofilaments having a diameter of at least about 0.1 millimeter. These structures have the flexural durability of traditional textile fabrics and the stiffness of large-diameter monofilaments. In addition, such structures have excellent resilience and cushioning properties. Unfortunately, the stiffness of the monofilaments which is essential to the cushioning and recovery of such network structures also gives the structures a harsh, rough hand. Thus, these structures tend to be uncomfortable against the skin. Another drawback of such structures is that they have little ability to control the movement of air or water.
Accordingly, one object of this invention is to provide a three-dimensionally shaped fiber network structure which has both resiliency and a softer, more pleasant touch or hand.
A further object of this invention is to provide a three-dimensionally shaped fiber network structure which has good cushioning properties in addition to resiliency and a softer, more pleasant touch or hand.
Another object of this invention is to provide a three-dimensionally shaped fiber network structure which has the aforementioned properties and also the capacity to selectively transport water from one side of the structure to the other side thereof.
An additional object of this invention is to provide a method of making a three-dimensionally shaped fiber network structure which has the properties set forth in the foregoing objects.
A still further object of this invention is to provide articles composed of three-dimensionally shaped fiber network structures having the properties set forth in the preceding objects.
These and other objects which are achieved according to the present invention can be readily discerned from the following description.